(1) Field of the Invention
It is widely recognised that safety is greatly increased if a vehicle has some form of alarm fitted which operates to warn people when the vehicle is reversing. This applies to many types of vehicles, including cars, vans, lorries, and buses, and also light and heavy mobile plant such as tractors, fork-lift trucks, dozers and loaders.
Such alarms typically take the form of either a light and/or an audible sound which is operated when the vehicle is put into reverse gear. Ideally, the alarm is activated automatically by engaging reverse gear. Previously proposed alarms have combined both light and sound, so that the presence of a reversing vehicle is apparent even if the vehicle is out of sight or if a person is not looking at it, and it also can be detected by both visually impaired and aurally impaired people.
(2) Description of Related Art
Previously proposed sound alarms have used a single tone sound, which may be pulsed to produce a beeping effect, or may be swept through a predetermined frequency range in the manner of alarms on emergency vehicles. Whilst such an arrangement is effective in being recognised as an alarm, partly due to the common usage of such sounds for that purpose, alarms using this feature have disadvantages.
The human brain is very poor at being able to locate the source of a sound which consists of a single frequency or just a few frequencies. Therefore, known reversing alarms will alert a person to the fact that a vehicle nearby is reversing, but will provide little guidance as to the location of the vehicle. This is clearly a significant problem, given that the vehicle could be obscured from view, by, for example, a building, other traffic, or boxes in a warehouse, or allowing for the fact that the person may be visually impaired. Thus, the impetus for the person to take appropriate evasive action is not as great as is desirable.
It is an aim of the present invention to address the aforementioned disadvantage.